NCATS has as an objective the affordable high throughput screening (HTS) of compounds to assess safety and mechanistic pathways perturbed by those compounds. This requires a broad assay covering the 1000 to 2000 pathways known today. RASL-Seq has the potential to provide a low cost assay of 1000 or more genes that can be performed in high throughput, as required of a screening assay, and permit pathways that are modulated and safety mechanisms that are perturbed to be identified . The requirements are to: i) implement commercial 384-well kits and a high throughput assay protocol for a RASL-Seq high throughput screen (HTS) measuring the Tox21 NCATS Hu l 400 set of genes; ii) implement the gene content of the Tox21 NCATS Hu l 400; iii) implement a mouse and a rat version of the Tox21 NCATS Hu l 400; iv) evaluate and validate improvements to the assay reagents and protocol and then implement these in the kits; v) evaluate protocol and hardware for, and if feasible and if doing so will reduce the cost/sample by at least 5-fold, implement kits for assay processing in 1536-well format; vi) automate the data analysis process; and vii) l ink the gene content to pathway databases to facilitate the interpretation of results.